Various types of aircraft frequently have an aerodynamically optimized shape in order to lower the fuel consumption and to improve the flying characteristics. Aircraft with a relatively high cruising speed usually have a rather elongate shape, but there also exist airborne vehicles with a shape that is not aerodynamically optimized for all needs despite a relatively high attainable cruising speed. This may now and then be the case with transport aircraft that not only need to fulfill a transport function, but also provide particularly effortless access to the cargo compartment and comprise, e.g., an upswept aft fuselage with a hatch door such that bulky goods, vehicles and the like can be easily introduced into the fuselage of the aircraft. Such aircraft occasionally comprise a landing gear that is arranged laterally of the actual fuselage underneath outwardly directed landing gear fairings. Among experts, the term “sponson” that was originally derived from shipbuilding is also used for such bulged shapes on a fuselage underside.
In transport aircraft with upswept aft fuselage, two pronounced main vortices with relatively high intensity are usually created in-flight. If the aircraft additionally comprises above-described sponsons that protrude into the air flow, additional vortices are created that rotate, for example, in the opposite direction referred to the two aforementioned main vortices and in combination with these main vortices lead to a complex vortex system. A deterioration of the directional stability, in particular, may be the direct consequence thereof and entail an increase in the aerodynamic drag.
U.S. Pat. No. 5,069,402 describes an airfreighter with upswept aft fuselage, in which vortex generators are arranged on an underside of the upswept aft fuselage in a region that is acted upon by the main vortices in order to reduce the aerodynamic drag of the transport aircraft.